MRI Quality Control Program

Yearly Performance Evaluation
and Acceptance Testing

Some
sites object to the need for the ACR’s QA program
which includes the need for yearly system performance
evaluations. However, I have currently set up QA programs
and performed the yearly performance evaluation on 20
magnets and have found it to be extremely useful. For
example, as part of the initial system checkout, I found
problems with the following RF coils:
4 CTL coils Anterior neck coil
3 Knee phased array coil 2 Flexible Body phased array coils
2 Shoulder phased array coils TMJ coil
3 Neurovascular coils Cardiac Phased Array
Extremity Coil 2 Peripheral Vascular Runoff coils
8-Channel Head coil
I also noted that four Medrad power injectors were overdue
for calibration, found 5 scan rooms with RF shielding tabs
broken off their doors and two scanners with severe geometric
distortion. As part of my initial visit to a site I now
check fringe fields. At the first site I made these measurements
I found a 40 square foot area outside of their building
with public access where the field ranged from 5 to 18
Gauss. At another site I found greater than 70 gauss in
a public region outside of the building!
Beyond identifying clearly deficient RF coils, one of the
most useful results of the yearly performance evaluation
is establishing baseline performance for all your coils.
Let’s say that 6 months after establishing this baseline,
you notice a possible loss in signal quality. Simply pull
out the most recent yearly report and repeat the testing
done at that time. If the SNR has dropped or ghosting has
increased you have a strong case to present to your service
engineer to have him fix or replace the coil.
Magnetic Resonance Imaging is more complicated than all
other imaging modalities combined. The scanners consist
of many components that all must be working together properly
in order to produce quality images. Although most sites
have a service engineer perform periodic preventive maintenance
(PM), these visits are usually very short and do not include
testing every RF coil present. These periodic PM visits
are analogous to changing your car’s oil every 3000
miles. A yearly performance can be compared to a complete
checkup with a mechanic every 12000 miles.
A site can easily spend more than a million dollars to
purchase and setup one of these scanners. The images obtained
can have a profound affect on that site’s patients.
A yearly performance evaluation is a small cost to pay
to help ensure that you, and your patients, get the most
from your investment.